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PUBLIC HEALTH ASSESSMENT

PEMACO MAYWOOD
MAYWOOD, LOS ANGELES COUNTY, CALIFORNIA


SUMMARY

The California Department of Health Services (CDHS) prepared this public health assessment (PHA) under a cooperative agreement with the Agency for Toxic Substances and Disease Registry (ATSDR). A PHA provides the community with information on the public health implications of specific hazardous waste sites and identifies those populations for whom further health actions or studies are indicated.

Pemaco Maywood is 4-acre site located at 5050 Slauson Avenue in Maywood, Los Angeles County, California. The area is mixed light industry-commercial-residential, with an exclusively residential neighborhood immediately south of the site. As with most of Maywood, this neighborhood is predominantly Latino; indeed, many of the residents are mono-lingual Spanish speakers.

Pemaco is a former chemical blending facility that operated from the late 1940s until 1991. A number of chemicals were used at this facility, including chlorinated and non-chlorinated solvents, aromatic solvents, flammable solvents, petroleum hydrocarbons, and other volatile organic chemicals (VOCs). Chemicals were stored in underground and above ground storage tanks. Waste materials were stored in approximately 400 55-gallon drums. In 1992, when members of the Los Angeles County Fire Department Hazardous Waste Program and the Los Angeles County District Attorney's Office visited the site, they observed open, unlabeled drums leaking material onto a concrete pad.

After a 1993 fire at the facility, the United States Environmental Protection Agency (USEPA) became involved with the site. In December 1993, the USEPA conducted a site assessment, finding 31 underground storage tanks and six aboveground storage tanks, but only six 55-gallon drums. The USEPA removed 30 of the underground storage tanks and decommissioned the remaining underground tanks in place. Soil samples were collected from sub-surface locations (5 feet deep) around the site and six deep boreholes (100 feet deep). Two of these deep boreholes were converted to monitoring wells, and two additional monitoring wells were drilled. In addition, 15 wells were drilled around the site to measure the level of contamination in perched groundwater beneath the site.

This sampling effort revealed that the subsurface soil beneath the site was contaminated with acetone, methyl ethyl ketone, 1,1,1-trichloroethane, trichloroethylene, methyl isobutyl ketone, ethylbenzene, xylene, and tetrachloroethylene. Samples collected from the boreholes were contaminated with acetone, 1,1-dichloroethane, 1,2-dichloroethylene, and trichloroethylene. Perched groundwater samples were contaminated with gasoline, benzene, chloroethane, 1,1-dichloroethane, 1,1-dichloroethylene, 1,2-dichloroethylene, ethylbenzene, tetrachloroethylene, toluene, 1,1,1-trichloroethane, trichloroethylene, vinyl chloride, and xylene. While the perched groundwater beneath the site is contaminated, this contamination does not appear to have affected any drinking water wells. Although several water companies maintain drinking water supply wells in the area of the site, they draw the water from deep aquifers. Nevertheless, one of these municipal wells has been contaminated from an unspecified source.

At the time of the initial writing of this PHA, many data gaps existed in the environmental sampling, such as off-site soil and soil gas sampling, and definition of the groundwater plume. Thus, it was not possible to evaluate potential adverse health effects to the community due to exposure to that contamination. In the initial PHA, we suggested that the most likely potentially completed exposure pathway is exposure to soil gas arising from shallow groundwater beneath the neighborhood south of the site. The soil gas can be pulled into buildings like houses, resulting in the occupants breathing the contaminants. We also concluded in this PHA that, because most of the chemicals used at the Pemaco facility were volatile, it is unlikely that significant contaminant levels would remain in surface soils.

Since initial writing of the PHA, the USEPA has overseen the completion of additional sampling efforts (this data is summarized in the Public Health Recommendations and Action Plan in this document). The additional data suggests that off-site surface soil is not an exposure concern and there is a possibility that low levels of acetone in the indoor air may be coming from the soil gas. Current levels in the indoor air do not represent a health hazard. It is important that the source of the soil gas be fully understood to ensure that future potential exposures are identified.

In addition to these current exposures, in this PHA, CDHS and ATSDR evaluated past exposure to chemicals coming from the soil gas treatment system. In 1999, the USEPA installed a soil vapor extraction system to remove soil gas on site. Part of this system included a thermal oxidizer, used to destroy soil gas vapors that were not trapped in the carbon filters of the vapor extraction system. The community, however, became concerned that the thermal oxidizer could have emitted chlorinated dibenzofurans and chlorinated dibdenzo-p-dioxins (dioxins). The USEPA shut down the thermal oxidizer and removed it from the site. Subsequently, community residents have expressed general, non-specific health complaints, but none have specifically implicated the Pemaco Site as the source of those complaints.

The exact emissions during operation of the thermal oxidizer are not known. After closure of the facility, a trial run of the thermal oxidizer measured concentrations of nine target compounds at the stack outlet. Dioxins, however, were not among the target compounds. An estimated emission rate, flow rate, and average meteorological conditions were used to calculate the off-site impact, based on the measurements at the stack outlet. The concentrations of contaminants that could have reached the residential neighborhood south of the site were estimated. Again, dioxins were not included. These are not measurements taken around the neighborhood, during operation of the thermal oxidizer. Rather, they are estimates based on measurements of target compounds at the stack outlet during three test runs. Based on this model, the maximum exposed individual is located approximately 100 meters north-northeast of the site in an area of low residential population. In addition, the concentration of contaminants from the stack was also modeled at the Heliotrope Elementary School, located a few blocks to the west of the site. In both locations (the maximum exposed individual and the Heliotrope Elementary School), the concentrations of contaminants are below those at which non-cancer adverse health effects would be expected to occur. They are also below the unit risk concentration, i.e., the concentration of a chemical at which one would see a 1 x 10-6 increase in the lifetime cancer risk.

Because the source of VOCs in the indoor air has not been fully characterized, CDHS and ATSDR classify the site as an indeterminate public helath hazard.


BACKGROUND

CDHS' Environmental Health Investigations Branch (EHIB) has prepared this PHA under a cooperative agreement with ATSDR. ATSDR, located in Atlanta, Georgia, is a federal agency within the United States Department of Health and Human Services (HHS). Among other responsibilities, ATSDR is authorized under the Comprehensive Environmental Response, Compensations, and Liability Act (CERCLA) of 1980, as amended, to conduct health assessments at hazardous waste sites on the National Priorities List (NPL).

This PHA evaluates the public health significance of the Pemaco Maywood Site, and is based on a review of environmental sampling data, site visits, and consultations with federal and state agencies and the public.


SITE DESCRIPTION AND HISTORY

The Pemaco Maywood site is a 4-acre site located at 5050 Slauson Avenue in Maywood, Los Angeles County, California (Figure 1), bounded on the north by Slauson Avenue, on the east by the Los Angeles River, on the south by 59th Street, and on the west by other industrial facilities (Figure 2). The area is a mixed business and residential area; a residential neighborhood is located south of the site, directly across 59th Street.

From the late 1940s to 1991, Pemaco, Inc. used the Pemaco facility to blend chemicals. A number of chemicals were used, including chlorinated solvents, aromatic solvents, flammable liquids, petroleum hydrocarbons, and other VOCs. These chemicals were stored in underground storage tanks (USTs) located on the south end of the site, in above ground storage tanks in the center of the site, and in 55-gallon drums located on the east side of the site (Figure 3) [1,2].

In May 1992, Los Angeles County Fire Department Hazardous Waste Program officers inspected the site and observed approximately 400 55-gallon drums. The drums contained waste product, many were in poor condition, open, unlabeled, and overflowing onto the concrete pad that covered most of the site. Areas of the concrete pad were stained and discolored with runoff from the drums. And the pad had cracks in it, so it was permeable to spilled materials. A former Pemaco employee identified 57 drums as containing chlorinated solvents. In August 1992, when representatives of the Los Angeles County District Attorney's Office visited the site, the drums were still there [1].

In 1993, after a fire destroyed the on-site warehouse, the USEPA became involved with the site. In December 1993, when the USEPA conducted a Site Assessment, six above ground storage tanks (ASTs) and 31 underground storage tanks (USTs) remained on the site, but only six 55-gallon drums remained. All of the USTs had apparently been emptied--only small quantities of residual liquids remained. In August 1997, the USEPA removed 30 of the 31 USTs and filled the remaining tank with concrete. As the tanks were removed, they were observed to be in relatively good shape; the connecting pipes and valves were the apparent sources of the leaks. But the Site Assessment revealed hazardous VOCs, including chlorinated and non-chlorinated solvents, had been released into the groundwater and soil beneath the site [1,2].

The Pemaco Site was nominated to the NPL (or Superfund List) after the EPA's assessment concluded the site posed a significant threat to human health, welfare, and the environment. The shallow groundwater beneath the site was found to be contaminated with chlorinated and non-chlorinated solvents. The nearest drinking water well is 0.4 miles away and another 14 drinking water wells servicing approximately 339,000 people are within 2 miles of the site [40].


SITE VISITS

CDHS staff members have visited the site twice. On January 8, 1999, Gina Margillo and Reber Brown examined the site from outside the fence. There are no structures on the site; most of it is covered by a concrete pad and it is surrounded by a fence. On the fence, signs in both English and Spanish warn that the property is a Superfund site. The fence appeared to be in good repair, with no signs of trespass. Although the site is adjacent to the Los Angeles River, it is fenced off to prevent access by the public. But storm drains from the site do lead directly to the river. The thermal oxidizer installed by the USEPA as a part of its emergency response actions was on the west side of the site, where several ASTs were once located.

Immediately to the west of the site, across the railroad tracks at 5920 Alamo, is the abandoned W. W. Henry Co. factory. The building has numerous broken windows, and a loading dock is at the east end, facing the Pemaco Site. Numerous chemicals were handled at this facility, some of which were also handled at the Pemaco Site. Community members have expressed concern about this facility.

The second site visit occurred in May 1999. Gina Margillo, Primitivo Rojas, and Reber Brown of CDHS conducted door-to-door interviews in the neighborhood south of the site. The condition of the site had not changed except that, in response to community concerns, the thermal oxidizer had been removed. The filters and valves of the vapor extraction system, however, remained.


DEMOGRAPHICS

According to 1990 Census data, 30 census blocks are either wholly or partially within a 1-mile radius of the site. The demographics of these blocks disclose a total population of 46,261 in 11,564 households, 23,776 of whom are male (51.4%) and 22,485 female (48.6%). Ethnic groups include 17,248 white (37.3%), 323 black (0.7%), 404 Native American (0.9%), 676 Asian-Pacific Islander (1.5%), and 27,610 other (59.7%). The total Hispanic population is 40,338 (87.2%). By age, the population includes 5,244 under five years of age (11.3%), 10,839 between 5 and 17 years (23.4%), 11,688 between 18 and 29 years (25.3%), 11,840 between 30 and 49 years (25.6%), 3,993 between 50 and 64 years (8.6%), and 2,657 over the age of 65 (5.7%) [3].


LAND USE NEAR THE SITE

The areas to the east of the Pemaco Site (across the Los Angeles River), north of the site, and west of the site along the north side of Slauson Avenue are primarily commercial or light industrial. The area southeast of the site along Walker and District Boulevard and west of the river is also light industrial. The areas to the west of the site on the south side of Slauson Avenue, and south of the site are primarily residential--several churches are located in the residential areas, and two elementary schools are within 1 mile of the site. The Heliotrope Elementary School is about four blocks to the west of the site on Slauson Avenue, and the Woodlawn Elementary School is just under 1 mile to the southwest of the site [1,2].

The Trust for Public Land, a private, national not-for-profit land conservation organization, is working with cities in the Los Angeles area to establish the Los Angeles River Greenway along the Los Angeles River. The City of Maywood and the Trust for Public Land are planning to develop the site as a public park for use by area residents [40].


NATURAL RESOURCE USE NEAR THE SITE

Surface Water

The Pemaco Site is adjacent to the Los Angeles River, and storm drains from the site lead directly to the river. The river, however, is not used for drinking water, and no sensitive environments such as fishing areas exist near the site [1].

Groundwater

The site is located in the Central Basin Pressure Area of the Central Basin of the Los Angeles Coastal Plain. The name describes the fact that the aquifers are confined by relatively impermeable layers of clay and silt [1].

A layer of perched (i.e., trapped) shallow groundwater is between 20 and 28 feet beneath the site, but is not continuous across the site. In addition, two water-bearing formations are beneath the site: the Lakewood Formation and the San Pedro Formation. The Lakewood Formation begins at approximately 80 feet below ground surface and extends to approximately 230 feet below ground surface. It comprises four different aquifers: Artesia, Exposition, Gage, and Gardenia. The San Pedro Formation comprises five aquifers: Hollydale, Jefferson, Lynwood, Silverado, and Sunnyside. The Hollydale and Jefferson Aquifers are of lesser importance than the other three. A number of wells in the area draw water from the Lynwood and Silverado aquifers. Beneath the site, these two aquifers are separate, but within approximately 2 miles of the site, they are in direct contact with each other. In the locations where the two are in contact, the water layer begins at about 350 feet below ground surface and extends to about 600 feet. The Silverado Aquifer, however, extends as far as 900 feet below ground surface. The Sunnyside Aquifer is the lowest aquifer of the San Pedro Formation. Although not in direct contact with the Silverado

Aquifer, water wells in the area provide artificial conduits between the aquifers. Most of the active drinking water wells within 2 miles of the site, for which information is available, are screened from about 528 feet below ground surface [1].

The Lakewood and San Pedro Formations are not in direct contact; the two formations are separated by a layer of clay between 53 and 140 feet thick. Although pollutants would probably not reach the San Pedro formation through natural conduits, it is possible that old wells are in the area for which no records exist. Such older wells, if not constructed or if not decommissioned properly, could provide a conduit by which contamination from upper aquifers could reach lower aquifers [1].

Municipal Drinking Water Wells

Twelve water companies operate drinking water wells within 4 miles of the site: the Maywood Mutual Water Company #1, the Maywood Mutual Water Company #2, the Maywood Mutual Water Company #3, the City of Vernon, the Tract 180 Water Company, the Tract 349 Water Company, the City of Huntington Park, the Southern California Water Company serving the Cities of Bell and Bell Gardens, the City of Southgate, the City of Downey, the Walnut Park Mutual Water Company, and the California Water Service East Los Angeles Water System. None of the wells are known to draw from the Lakewood Formation, but it is possible that all wells draw from the San Pedro Formation. One of the wells has had a low level of contamination. This contamination, however, has not been attributed to the Pemaco Site [1].


HEALTH OUTCOME DATA

At various meetings community members have expressed health concerns, but the concerns have been relatively nonspecific. No one named the Pemaco Site as the source of those concerns. It should be noted, however, that in this PHA only completed exposure pathways will be assessed for public health effects. CDHS has not conducted any search of health-related data such as the California Birth Defects Monitoring Program or California Cancer Surveillance Program. No attempt was made during the preparation of this public health assessment to obtain data on past work practices at the Pemaco facility, occupational safety and health reports, industrial hygiene sampling records, or other information that would be required to prepare a retrospective exposure assessment for former employees.


COMMUNITY HEALTH CONCERNS

A heavily populated residential area is across the street from the Pemaco Site, and the City of Maywood estimates that approximately 98% of that population is Latino. In February of 1999, CDHS began its community outreach and involvement efforts by talking to residents at an USEPA public meeting. In 1998, after USEPA installed a thermal oxidizing unit as an emergency response effort, community members began to hear about the site. Community-based organizations such as Greenaction, the Del Amo Action Committee, and the Zero Tolerance Dioxin Alliance had raised concerns in the Maywood Community about the release of dioxin from the thermal oxidizer. Residents at that February meeting expressed concerns about dioxin. Some of the other health concerns included diabetes, asthma, allergies, and upper respiratory ailments. Residents questioned the safety of eating eggs from privately raised chickens or fruits and vegetables from their gardens. They also questioned the safety of the air and drinking water.

In April 1999, CDHS developed an informal list of questions in both Spanish and English for Communities for a Better Environment to distribute to residents at its meetings. To date, CDHS has not received any responses.

In May 1999, CDHS used the same list to conduct door-to-door interviews with 19 community members in homes close to the site. The residency period of those to whom CDHS spoke ranged from 8 months to 38 years. Seventeen interviewees had young children. Four interviewees reported raising their own fruits or vegetables on their property. No one reported raising chickens; everyone used water supplied by the City of Maywood. Roughly one-half of those interviewed had heard about the Pemaco Site, but no one reported any health concerns. Most said they would like to be kept informed about future meetings. Five preferred to be notified about future Pemaco meetings and provided their names and phone numbers. Those who preferred to be notified by mail provided only their names and addresses. Some preferred not to provide any type of identifying information.

CDHS also met with three teachers, one school nurse and the vice-principal of Heliotrope Elementary School--the school is four blocks away from the Pemaco Site. Two teachers reported their allergies had worsened since they began working at the school. They also reported a higher than average rate of allergies, colds, and other illnesses in their students, as well as various cases of asthma. Their concerns also extended beyond the Pemaco Site to include the general traffic and air pollution issues that stem from living in an industrialized area.

A common complaint among the residents and teachers at the Heliotrope Elementary School was the tap water. When filling a glass from the tap, they report the water has a distinctly unpleasant odor, and a slowly dissipating layer of bubbles appears on the water surface. Many have complained about the water to their water company, the Maywood Mutual Water Company #3, but have been told the water is fine.

Community relations activities included: 1) community interviews, 2) distribution of the health concerns questionnaire to parents of children who attend Heliotrope Elementary School, and 3) meetings with community-based organizations. Because no information forms were returned to CDHS, this method of collecting community information has been unsuccessful.


ENVIRONMENTAL CONTAMINATION

In this section, CDHS and ATSDR summarize the environmental data that was reported in documents up until 1998. Since that time, USEPA has overseen the collection of additional data and completion of the Remedial Investigation/Feasibility Study. This new data is briefly summarized in the Public Health Activities and Recommendations Plan in this document.

Identification of Contaminants of Concern

To assess the potential adverse health effects of environmental contamination on a nearby population, one must first identify the pollutants possibly affecting that population. Pollutants so identified are known as contaminants of concern and are identified using screening values for non-cancer and cancer effects.

Screening Values

The concentration of the contaminant in a specific medium (soil, air, water) is compared to ATSDR, USEPA, or state screening value. The screening value is the concentration of a specific chemical in a specific medium (soil, air, water) at or below which a person could be exposed, without the expectation of adverse health effects. Screening values are calculated using health-protective assumptions regarding the body weight and ingestion rate of the receptor population. Thus, if the concentration of the contaminant is below the screening value, one should feel confident that adverse health effects should not occur. If the concentration of the contaminant exceeds the screening value, it becomes a contaminant of concern. A contaminant could also become a contaminant of concern solely because of community concerns about it. Regardless, adverse health effects do not automatically occur if the concentration of a chemical exceeds its comparison value. The chemical must be further evaluated on an individual basis to determine the likelihood of exposure and the possibility of adverse health effects.

ATSDR uses screening values for both cancer and non-cancer adverse health effects. These screening values are described below.

Screening Values for Non-Cancer Adverse Health Effects

The primary screening value ATSDR uses for non-cancer adverse health effects is an Environmental Media Evaluation Guide (EMEG). An EMEG is a concentration of a chemical in soil, air, or water, above which a person exposed to might experience adverse health effects. EMEGs in soil and water are based on a Minimal Risk Level (MRL)--the daily dose (milligrams per kilogram per day [mg/kg/day]) of a chemical to which a person could be exposed without experiencing adverse health effects. MRLs, in turn, are usually derived from animal exposure studies, though some are calculated from human exposure studies. MRLs can be calculated for different lengths of exposure: acute (0 to 14 days), intermediate (15 to 364 days), and chronic (365 days and more), and for different routes of exposure (inhalation or ingestion).

EMEGs are calculated for both children and adults and are based on default values of body weight. If soil is incidentally ingested, the amount of that soil is included, as is the amount of water drunk each day and the volume of air inhaled each day. Also, some children exhibit so-called pica behavior; that is, they have a propensity to eat non-food items such as soil, sand, clay, ashes, and other similar substances. The amount of soil eaten by pica children is estimated at 5,000 milligrams per day (mg/day), as opposed to the average of 200 mg/day consumed by a child who does not exhibit pica behavior. This increased amount puts them at greater risk for adverse health effects from ingesting contaminated soil (the EMEG is correspondingly lower for pica children).

If no MRL or other similar value exists for a chemical, then other values are used. Most frequently, ATSDR will use the USEPA reference dose (RfD) for that chemical. The RfD is analogous to ATSDR's chronic MRL. Other comparison values used in the absence of an MRL or RfD include USEPA Preliminary Remediation Goals (PRGs), drinking water Maximum Contaminant Levels (MCLs), state MCLs, and other state values.

Chemicals for which inhalation is the route of exposure are handled differently. Inhalation MRLs are expressed as the concentration of that chemical in the air, rather than as a dose of that chemical. EMEGs are not calculated for these chemicals, as the MRL is also used as a screening value. The same MRL is used for both adults and children.

Screening Values for Carcinogenic Adverse Health Effects

The screening value ATSDR uses to identify carcinogenic contaminants of concern is a Cancer Risk Evaluation Guide (CREG). A CREG is the concentration of a chemical in a specific medium (air, soil, water) expected to cause a greater than 1 x 10-6 increase in the lifetime cancer risk if ingested or inhaled. CREGs are derived from the USEPA or state slope factor, or cancer potency factor for that chemical.

In an average population of 1,000,000 persons, approximately 250,000 will, due to various factors, develop cancer during their lifetime. In other words, about 25% to 35% of Americans will develop cancer. When considering the increased lifetime cancer risk, one must understand that this value represents the expected increase in the number of cases of cancer, over and above the normal background rate of cancer, i.e., 25% - 35%. An increased lifetime cancer risk of 1 x 10-6 means that in that same population of 1,000,000 people, 250,001 will develop cancer at some point in their lives, with the extra one case arising from the specific chemical exposure under evaluation.


ON-SITE CONTAMINATION

At one time, 31 underground storage tanks, 6 above ground storage tanks, and as many as 400 55-gallon drums were on the Pemaco Site. The 31 underground tanks contained 21 different chemicals (Table 1). When they were removed in August 1997, the tanks were reported to be in generally good shape. The connecting pipes and valves appeared to be the source of the leaks that caused the subsurface soil and groundwater contamination described below [1].

For the most part, the drums were unlabeled and many were open or leaking. They are believed to have contained various waste products. Fifty-seven drums were identified by a former Pemaco employee as containing chlorinated solvents. A concrete pad, approximately 1-foot thick, covers much of the site. But the pad had fractures and was discolored in several locations. The discolored locations are attributed to leaks from open or damaged 55-gallon drums. There was no spill containment system, so spills onto the pad could flow to the storm drains and ultimately to the Los Angeles River. Fractures in the pad provided a conduit for leaked material on the pad to reach the soil below, and ultimately, the groundwater below the site. The 1992 Hazardous Material Business Plan filed with the Los Angeles County Fire Department in June 1992--after the site closed--listed several types of wastes stored on site (Table 2), but with no indication of where on the site the various chemicals were stored. By December 1993, however, only six drums remained on site [1].

On-Site Subsurface Soil

In 1990, a Pemaco contractor conducted a subsurface soil investigation on the site. Contamination in the soil in the vicinity of the storage tanks included acetone, methanol, ethanol, methyl ethyl ketone, methyl isobutyl ketone, methylene chloride, tetrachlororethylene, ethylbenzene, toluene, and xylene. No information from this study, concerning the concentrations of these chemicals in the soil near the underground storage tanks or the limits of detection for those chemicals, is available [1]. In 1997, as part of the Expanded Site Inspection, 16 subsurface soil samples (5 feet below ground surface) were collected and analyzed for volatile organic compounds. Chemicals identified in these samples at greater concentrations than their respective limits of detection include acetone, methyl ethyl ketone, trichloroethane, trichloroethylene, tetrachloroethylene, methyl isobutyl ketone, toluene, ethylbenzene, and xylenes. The concentrations of these chemicals are listed in Table 3 [1].

These data show that acetone was detected in almost all of the subsurface soil samples. The highest levels of contamination, however, are at the southwest side of the site, just to the south of the ASTs' former location, and in the central area of that site, also close to where the ASTs were located. In the southwest side of the site, the highest levels of contamination were collected from location NSB-105 (Figure 3). At NSB-105, the concentration of acetone is 79,000 micrograms per killigram (µg/kg), methyl ethyl ketone is 12,000 µg/kg, and methyl isobutyl ketone is 2,700 µg/kg (estimated concentration). The concentration of ethylbenzene is 2,100 µg/kg (estimated concentration), xylene is 15,000 µg/kg, and tetrachloroethylene is 210 µg/kg (estimated concentration). In the central area of the site, the highest levels of contamination were found in locations NSB-109 and NSB-110. Acetone, methyl ethyl ketone, methyl isobutyl ketone, ethylbenzene, and xylene were detected in NSB-109. Acetone and methyl ethyl ketone were detected in NSB-110. But in NSB 105, 109, and 110, the concentrations of these contaminants are all less than their respective EMEGs (Table 3).

Only a limited possibility of contact with the subsurface contamination exists and virtually no possibility of contact with deeper soils. It is very unlikely that vapors of these volatile chemicals could reach the air above the site through cracks in the concrete pad in sufficient concentration to represent a health threat. Nevertheless, it is possible this contamination could travel down through the soil to shallow groundwater beneath the site, then to drinking water aquifers also beneath the site. Thus, even though the concentrations of these contaminants are below their respective EMEGs for soil exposure, the chemicals are considered contaminants of concern because of their potential to reach the groundwater beneath the site.

In addition to these subsurface soil samples, six boreholes were drilled to a depth of about 100 feet. Soil samples collected approximately every 10 feet were analyzed for volatile organic chemicals. The depth of detection ranged from 20 to 60 feet, with a few deeper samples. A few sporadic hits occurred. Chemicals detected in these samples at greater concentrations than their respective limits of detection include acetone, 1,1-dichloroethane, total 1,2-dichloroethene, and trichloroethylene (Table 4). None of the contaminant levels exceed their EMEGs. Matrix effects in some of these samples could potentially mask the presence of some pollutants. Two of these boreholes were later converted to monitoring wells (MW-1, MW-2, see Figure 3) [1]. These data show that the highest levels of contamination in deep soil are located in the southwest corner of the site and, to some degree, the southeast corner of the site.

No contamination was measured in the samples collected from MW-1. In MW-2, the highest concentration of acetone was estimated to be 2,300 µg/kg at 20 feet below ground surface. The concentration of 1,1-dichloroethane was an estimated 34 µg/kg at 10 feet below ground surface. The highest concentration of 1,1-dichloroethylene was 160 µg/kg at 10 feet below ground surface. The highest concentration of trichloroethylene was an estimated 120 µg/kg at 80 feet below ground surface.

In subsurface boring-1 (SSB-1), the concentrations of acetone, 1,1-dichloroethane, and trichloroethylene in all of the samples collected were non-detect. The concentration of 1,2-dichloroethylene was an estimated 61 µg/kg at 40 feet below ground surface.

In SSB-2, the highest concentration of acetone was an estimated 670 µg/kg at 6 feet below ground surface. The concentration of 1,1-dichloroethane was an estimated 37 µg/kg at 40 feet below ground surface. The concentration of trichloroethylene was 85 µg/kg at 40 feet below ground surface, and was non-detect in the samples collected from other depths.

In SSB-3, the highest concentration of acetone was 17,000 µg/kg at 30 feet below ground surface. The concentration of 1,2-dichloroethylene was an estimated 30,000 µg/kg at 15 feet below ground surface. The concentration of trichloroethylene was 1,200,000 µg/kg at 15 feet below ground surface.

In SSB-4, the concentration of acetone was an estimated 510 µg/kg at 30 feet below ground surface. The concentration of 1,2-dichloroehtylene was an estimated 18 µg/kg at a depth of 30 feet below ground surface. The highest concentration of trichloroethylene was 990 µg/kg at a depth of 80 feet below ground surface.

On-Site Groundwater

A layer of perched groundwater is beneath the Pemaco Site. A layer of clay perches the groundwater between 26 to 31 feet below ground surface. Information on the well characteristics of the perched groundwater wells is shown in Table 5. The perched groundwater is contaminated with the following volatile organic compounds from the site: benzene, chloroethane, 1,1 dichloroethane, 1,1 dichloroethylene, 1,2 dichloroethylene, ethylbenzene, tetrachloroethylene (PCE), toluene, 1,1,1 trichloroethane, vinyl chloride, and xylene. The concentration of contamination in the perched groundwater is listed in Table 6 [1]. A layer of free product, identified as gasoline, has been found in several of the wells.

No obvious pattern emerges regarding contamination in the perched groundwater. The highest concentration of benzene is 170 micrograms per liter (µg/L) at well B-7-P (east central side of site). The concentration of chloroethane is highest at 58 µg/L in well B-15-P (west central side of site). The highest concentration of 1,1-dichloroethane is 170 µg/L at well B-8-P (east central side of site). The concentration of 1,1-dichloroethylene was 36 µg/L at well B-1-P (east central side of site). The highest concentration of 1,2-dichloroethylene is 350 µg/L at well B-1-P. The highest concentration of ethylbenzene is 270 µg/L at well B-8-P. The concentration of PCE was 22 µg/L at well B-1-P. The concentration of toluene is highest at 200 µg/L at well B-1-P. The highest concentration of trichloroethane was 90 µg/L at well B-1-P. The concentration of trichloroethylene was highest at 180 µg/L at well B-12-P (south side of site). The highest concentration of vinyl chloride was 290 µg/L at well B-8-P (east side of site). The highest concentration of xylene was 720 µg/L at well B-4-P (central area of site).

Several VOCs in the perched groundwater exceeded health based comparison values. If this groundwater moves, especially if it moves in a southerly direction, the contamination in the groundwater possibly could produce soil gas in homes near the site. The clay layer is not continuous across the site, so the contaminated groundwater could potentially migrate deeper. This contamination could also reach deeper aquifers used for drinking water. Therefore, despite the fact that the concentrations of most of these contaminants are less than their respective EMEGs and MCLs, these chemicals remain as contaminants of concern.

On-Site Surface Water

No surface water is on the Pemaco Site.


OFF-SITE CONTAMINATION

Municipal Water

CDHS assumes that all of the homes in the neighborhood near the Pemaco Site use municipal water. This assumption is based on interviews with neighborhood residents and on conversations with staff members of the Los Angeles office of the California Office of Drinking Water and Environmental Management, and the Los Angeles County Department of Health Services. Three water companies, Maywood Mutual Water Company #1 (MMWC#1), Maywood Mutual Water Company #2 (MMWC#2), and Maywood Mutual Water Company #3 (MMWC#3), service the City of Maywood and parts of nearby cities [4-6]. The wells for MMWC#1 and MMWC#2 are all in compliance with primary drinking water standards [4,5]. Nevertheless, both wells of MMWC#2 exceed secondary drinking water standards for manganese, and one of its wells exceeds secondary drinking water standards for iron [5]. Primary drinking water standards are health-based standards. Secondary standards are concerned with aesthetic qualities of drinking water, such as odor and taste. MMWC#2 treats the water from its wells to remove the manganese and iron from its water.

The Pemaco Site and the neighborhood to the south are serviced by MMWC#3. According to the latest Annual Inspection Report for this water company, in early 1999, trichloroethylene was detected in Well #3. But the concentration of trichloroethylene in Well #3 was 2.3 µg/L, below its maximum contaminant level (MCL) of 5 µg/L (6).

According to the Annual Inspection report for MMWC#3, this well is 1,333 feet deep. Its highest perforation is approximately 350 feet deep, the approximate depth of the upper part of the San Pedro Formation [1]. In addition, the well is located to the east of Maywood in the City of Bell [6]. Given that the groundwater in the vicinity of the Pemaco Site flows in a generally south to southwest direction [1], CDHS considers it unlikely that the Pemaco Site is the source of contamination in this well.

Groundwater and Soil Gas Beneath the Neighborhood South of the Site

At the time of the initial writing of this PHA, CDHS had no data for shallow groundwater or soil gas beneath the neighborhood to the south of the site. As discussed above, CDHS assumes the homes in the neighborhood south of the Pemaco Site use municipal water and that no active private wells operate in the neighborhood. An examination of the report Watermaster Service in the Central Basin Los Angeles County of October 1998 shows no private wells in Maywood [7] (Personal communication between F. Reber Brown, California Department of Health Services, and Jack Petralia, Los Angeles County Department of Environmental Health; June 1, 1999).

W.W. Henry Site Groundwater

The site immediately to the west of the Pemaco Site is the abandoned W.W. Henry Co. factory. W.W. Henry used some of the same chemicals as the Pemaco facility. Groundwater and soil gas samples have been taken from this site, and according to a private screening report, "free hydrocarbon product (FHP) has been observed on perched groundwater in monitoring wells on the eastern portion of the site" [3]. The principal component of this FHP was identified as toluene. CDHS is not able to verify the source of this contamination.

Surface Water

The only surface water in the area is the Los Angeles River. CDHS has no data for the levels of contamination for the part of the Los Angeles River channel between the site and the Los Angeles River. An embankment separates the site and the river, but no berms or other containment measures exist on the Pemaco Site, and the storm drains onsite lead directly to the river. Thus, contamination from the Pemaco Site could have reached the Los Angeles River by leaking from drums or storage tanks on the site and into the storm drains leading to the river. Nonetheless, the river is not used for drinking water, and no fishing is allowed in the area. Moreover, although contamination present in the river could have originated from the Pemaco Site, it could also have originated from other industrial facilities in the area [1,2].

Surface Soil of the Homes of Nearby Residents

At the time of the initial writing of this PHA, CDHS had no data for the levels of contamination in the surface soils of homes near the Pemaco Site.

Home-Grown Produce and Home-Grown Animals of Nearby Residents

CDHS has no data for the concentration of contaminants in or on home-grown fruits or vegetables or in domestic animals near the Pemaco Site.

Airborne Contamination

CDHS has no data for the concentration of airborne contamination in the vicinity of the Pemaco Site. The two primary sources of airborne contamination on the Pemaco Site were: 1) fugitive vapors from leaking storage tanks and drums carried by the wind to the nearby neighborhood and 2) emissions from the thermal oxidizer stack. The drums and tanks have been removed, and the thermal oxidizer has also been shut down and removed. Thus, no current sources of airborne contamination persist on the site.

Thermal Oxidizer Emissions

Similarly, CDHS has no data from the neighborhood for the thermal oxidizer contaminants. The emissions from the oxidizer stack have been modeled to assess the potential public health impact of oxidizer emissions [2]. The results are based on target compound levels at the stack outlet during three test runs. Dioxins were not included in this analysis. Modeling only provides an estimate of the levels of pollution from the thermal oxidizer stack. A detailed description of the modeling process is in the Toxicological Evaluation section.

To evaluate whether persons near the site might have been exposed to significant levels of contamination from the thermal oxidizer, the concentrations of contaminants in the emissions from the thermal oxidizer stack were modeled for a series of ambient locations, including the neighborhood south of the site. The concentrations of the emissions from the thermal oxidizer at two specific locations near the site are listed in Appendix C [2]. The Maximum Exposed Individual (MEI) is the person exposed to the highest levels of contamination from the thermal oxidizer emissions. The MEI is located approximately 100 meters north-northeast of the site. The concentrations of contamination at the Heliotrope Elementary School were also modeled (Appendix C).


QUALITY ASSURANCE/QUALITY CONTROL PROCEDURES

In preparing this PHA, CDHS relies on the information provided in the referenced documents and assumes adequate quality assurance and quality control measures were followed with regard to chain of custody, laboratory procedures, and data reporting. The accuracy of the conclusions contained in this PHA is determined by the completeness and reliability of the referenced information.


PHYSICAL AND OTHER HAZARDS

No extraordinary physical or other hazards were observed on or near the site during CDHS site visits. A fence surrounds the site; it appears to be intact and warning signs in both English and Spanish are posted on it. During CDHS's first visit, the thermal oxidizer was located within the fence line of the site and so was not accessible to those outside of the fence. The thermal oxidizer has since been removed.

Slauson Avenue, on the north side of the site, is a major thoroughfare with heavy car and truck traffic. On the south side of the site, 59th Street runs to the west and forms the north side of the residential area. District Boulevard and Walker Avenue run parallel to the Los Angeles River, between the river and the neighborhood, and into the southeast corner of the site. Walker Avenue and District Boulevard both contain industrial facilities and associated truck traffic. Streets near the Heliotrope Elementary School and 59th Street also carry truck traffic. Neighborhood residents and teachers at the school specifically mentioned truck traffic as a hazard to area children (see Figure 3).


PATHWAY ANALYSIS

For a receptor population to be exposed to environmental contamination, a mechanism known as an exposure pathway must connect that contamination with the target population. An exposure pathway consists of five parts:

  1. a source of contamination,
  2. an environmental medium and transport mechanism,
  3. a point of exposure,
  4. a route of exposure, and
  5. a receptor population.

Exposure pathways are classified as completed, potential, or eliminated. A completed exposure pathway is one in which all five elements of the pathway are present. A potential pathway is one in which one or more elements of the pathway are missing but might have been present or might be present later. A pathway can also be described as a potential pathway if information on one of the elements of the pathway are missing. An eliminated pathway is one in which one or more of the elements are missing and will not be complete in the future. For a population to be exposed to an environmental contaminant, a completed exposure pathway (all five elements) must be present. If any one or more of these elements are missing, then no exposure is present, though contamination could still be substantial and require remediation. This is especially true if an incomplete exposure pathway could become complete in the future.

Completed Exposure Pathways

Inhalation of Thermal Oxidizer Stack Emissions by Adults and Children

CDHS has identified one complete exposure pathway (Table 9): adults and children inhaling stack emissions from the thermal oxidizer on the site. CDHS is not aware of any direct measurements of the concentration of airborne contamination from the thermal oxidizer stack during its functioning. Nevertheless, the concentration of these airborne contaminants has been modeled by computer, using data from three test runs, and estimates of emission rate and flow rate. Modeling is a mathematical method of estimating the concentration of a chemical in a medium (air, water, soil, food) taking into account how the chemical was released into the environment and, once in the environment, how the chemical would travel. Although the thermal oxidizer was shut down during the spring of 1999, these modeled concentrations represent estimates of relatively recent exposures to these contaminants. Therefore, CDHS evaluated these exposures as a past but completed exposure pathway.

This exposure pathway assumes that adults and children were exposed to contaminants from the thermal oxidizer stack. Concentrations of contaminants from the thermal oxidizer stack were modeled for a series of locations around the site. In addition, the concentration of contamination was also modeled at the Heliotrope School.

Potentially Completed Exposure Pathways

CDHS determined there are two potential exposure pathways (Table 10).

Adults and Children Exposed to Contamination Through Inhalation of Soil Gas from Shallow Groundwater

The exposure pathway assumes that adult and child residents of the neighborhood to the south of the Pemaco Site are exposed to contamination from the site through the inhalation of soil gas from contaminated shallow groundwater. The pathways are considered potentially completed because whether the shallow groundwater is contaminated is currently unknown. No data is available on the shallow groundwater beneath the homes in the neighborhood south of the Pemaco Site. If the shallow ground water is contaminated (less than 33 feet deep) beneath the neighborhood to the south of the site, vapors from volatile contaminants in that shallow groundwater can potentially pass through the soil and into buildings above. These vapors, known as soil gas, are a potentially substantial source of contamination in buildings.

Additional soil gas and indoor air sampling conducted in the neighborhood by the USEPA has indicated a possible migration of acetone from the groundwater. This is still being investigated (see Public Health Actions and Recommendations Section).

Adults and Children Exposed to Contamination Through Inhalation of Fugitive Vapors from the Storage Tanks and Drums on the Site

This exposure pathway assumes that adult and child residents of the neighborhood to the south of the site were exposed in the past to contamination from the Pemaco Site through the inhalation of fugitive vapors emanating therefrom. The source of these vapors includes the storage tanks and the 55-gallon drums formerly on the site. These pathways are considered potentially completed because it is unknown whether vapors from storage tanks and drums on the site actually migrated offsite, or what the concentration of those vapors might have been, had they migrated.

Exposure Pathways Not Considered or Eliminated

CDHS eliminated several pathways from further consideration (Table 11).

Adults and Children Exposed to Contamination Through Incidental Ingestion of Contaminated Surface Soil

This exposure pathway assumes adult and child residents of the neighborhood to the south of the Pemaco Site are exposed to contamination from the site through the incidental ingestion of contaminated surface soil. Incidental ingestion occurs accidentally while engaging in other activities such as gardening. At the time of the initial writing of this PHA, this pathway was considered potentially completed because no off-site surface soil sampling had yet occurred. Airborne contaminants from the Pemaco Site could have reached the yards of homes near the site primarily by windborne contaminated materials from the site falling to the ground off site. Because almost all of the chemicals handled at the Pemaco Site were volatile (i.e., chemicals that evaporate easily), it is unlikely that substantial amounts of these chemicals would remain in the surface soil of neighborhood yards south of the Site. Nevertheless, low-volatility chemicals (chemicals that do not evaporate easily) such as chlorinated dibenzofurans and chlorinated dibenzo-p-dioxins that may have been emitted from the thermal oxidizer emissions could be found in the surface soil.

More recent data collected by USEPA does not indicate that nearby residential surface soil is contaminated, thus this pathway is considered eliminated.

Adults and Children Exposed to Contamination Through Ingestion of Contaminated Home-Grown Produce or Home-Grown Animals

This exposure pathway assumes adult and child residents of the neighborhood to the south of the Pemaco Site are exposed to contamination from the site through the ingestion of contaminated home-grown produce, including both garden produce and fruit trees, or through the ingestion of domestic animals. These exposure pathways are considered to be a potentially completed exposure pathways because it is unknown how many, if any, residents consume fruits and vegetables from their gardens or fruit trees and/or raise animals for food. It is also unknown whether any of these food sources are contaminated. Contamination could have reached home-grown produce in the yards of nearby residents in the same manner it reached the surface soil, namely, deposition of airborne contamination from the Pemaco Site onto produce in gardens and onto fruit trees. In addition, if water used to irrigate these trees or gardens is contaminated, fruit or vegetables could take it up and residents could ingest it. Also, domestic animals such as chickens can become contaminated. But because almost all of the chemicals handled at the Pemaco Site were volatile chemicals, it is unlikely that substantial amounts of these chemicals would remain in the surface soil of the yards in the neighborhood south of the Site.

Based on the lack of contamination found in nearby residential surface soil, this pathway is now defined as eliminated.

Adults and Children Exposed to Contamination Through Ingestion of Shallow Groundwater in Private Well Water

A staff member of the Los Angeles County Department of Health Services states that no private or small provider wells are in the area, but he also stated that some very old private or agricultural wells, for which no records exist, could still remain in the neighborhood (Personal communication between F. Reber Brown, California Department of Health Services, and Jack Petralia, Los Angeles County Department of Environmental Health; June 1, 1999). If such wells exist in the area, are in use, and draw water from contaminated groundwater, they could be a source of exposure contamination. Such wells could also be potential conduits by which contamination in shallow groundwater could reach deeper groundwater.

Additional pathways CDHS eliminated from consideration are:

  1. children and adults exposed to site-related contaminants in municipal water,
  2. children and adults who trespass into the Los Angeles River channel and become exposed to contamination from the site in the channel, and
  3. children and adults who trespass onto the site and become exposed to on-site contamination.

These pathways were eliminated because municipal water in the area is not contaminated above USEPA MCLs, and because access to the site and the river channel is restricted. During their site visits, CDHS staff did not observe anyone trespassing in the river channel, and no one CDHS interviewed reported seeing people in the river. While CDHS understands that children do play in the river on occasion, this does not appear to be a problem near the Pemaco Site. No current evidence suggests that individuals have actually trespassed into these restricted areas, and no one has reported seeing anyone trespassing into these areas.


PUBLIC HEALTH IMPLICATIONS

Toxicological Effects of Chemicals from the Pemaco Site

This section contains background information and toxicological effects of the chemicals of concern. The chemicals in this section are listed as measured in the soil or groundwater of the site and as chemicals evaluated in the assessment of the thermal oxidizer.

Acetone [8-11]

  • Naturally occurring chemical, also synthetically produced
  • Evaporates quickly in air, mixes readily with water
  • Used to produce other materials, also used as a solvent
  • Small amount of acetone made normally by the body
  • Can enter body through inhalation, ingestion, and dermal contact
  • Intermediate, chronic inhalation MRL = 13 ppm (30,900 µg/m3) (neurological effects in humans)
  • Intermediate oral MRL = 2 mg/kg/day (loss of white blood cells in rats)
  • Reference dose = 0.1 mg/kg/day (liver and kidney effects in rats)

Benzene [9-11, 13, 38]

  • Naturally occurring chemical, also in top 20 (by volume) of chemicals produced in the U.S.
  • Used in a wide range of products and industrial processes
  • Found in environment as a result of both human and natural processes
  • Degrades relatively quickly in air, slowly in soil or water
  • Does not bioaccumulate
  • Enters body through inhalation, ingestion, and dermal absorption
  • Adverse health effects due to intermediate or chronic exposures include disruption of blood production and possible reproductive problems in women
  • Intermediate inhalation MRL = 0.004 ppm (12.8 µg/m3) (neurological effects in mice)
  • Known human carcinogen
  • Oral slope factor = 2.9 x 10-2 (mg/kg/day)-1
  • Inhalation unit risk = 2.9 x 10-5 (µg/m3)-1

Carbon Tetrachloride [9-11, 14, 38]

  • Synthetic chemical
  • Widely used as a degreaser, spot remover, and in other products
  • Liquid at normal temperatures but evaporates easily
  • In soil, evaporates or goes to groundwater
  • Can enter body through inhalation, ingestion, and dermal contact
  • Adverse health effects due to short-term, high -level inhalation include decreased liver and kidney function, as well as nervous system effects such as headache, dizziness, and sleepiness
  • Effects of carbon tetrachloride increase if alcohol is consumed
  • Intermediate inhalation MRL = 0.05 ppm (315 µg/m3) (liver effects in rats)
  • Intermediate oral MRL = 0.007 mg/kg/day (liver effects in rats)
  • Chronic oral reference dose = 0.0007 mg/kg/day (liver effects in rats)
  • Probable human carcinogen
  • Oral slope factor = 0.13 (mg/kg/day)-1
  • Inhalation unit risk = 4.2 x 10-5 (µg/m3)-1

Chlorinated Dibenzo-p-Dioxins (CDDs) [9-11,15, 38]

  • Term CDD refers to a group of 75 related chemicals (called congeners) divided into eight subgroups, based upon number of chlorine atoms attached
  • 2,3,7,8-tetrachlorodibenzodioxin (2,3,7,8-TCDD) is most well known and most toxic form of PCDDs
  • Formed as a by-product of several industrial processes, also formed during combustion
  • Often found in environment with structurally related chemicals known as polychlorinated dibenzofurans (CDFs)
  • Forms containing fewer chlorine atoms can vaporize and become airborne
  • Forms with more chlorine atoms settle more quickly or stick to surfaces of particulate matter for eventual deposition on land or in water
  • Does not easily dissolve in water and tends to adhere to soil particles
  • Does not break down easily in air, water, or soil
  • Bioaccumulates in the food chain
  • Wide distribution in the ecosystem means that most people and animals have very low background levels in their fatty tissue
  • Continued exposure to CDDs can cause accumulation in fatty tissue over time
  • Most exposure occurs through ingestion of food contaminated with very small amounts of CDDs
  • Can enter body through inhalation, dermal contact, or most commonly, ingestion
  • Adverse health effects in animals difficult to determine. Some forms, especially 2,3,7,8-TCDD, are extraordinarily toxic to some species but not very toxic to other species
  • In general, adverse health effects in animals include chloracne, changes in blood cells, weakening of the immune system, reproductive effects, and cancer
  • Chronic oral MRL = 1.x 10-6 µg/kg/day (1 x 10-9 mg/kg/day, altered behavior in monkeys)
  • Probable human carcinogen.
  • Oral slope factor (2,3,7,8-TCDD) = 1.3 x 10-5 (mg/kg/day)-1
  • Inhalation unit risk (2,3,7,8-TCDD) = 38 (µg/m3)-1

Chlorobenzene [9-11, 16]

  • Naturally occurring chemical, also synthetically produced
  • Used as a solvent and in production of other chemicals
  • Breaks down very quickly in water, relatively quickly in air, slowly in soil
  • Can enter body through inhalation, ingestion, and dermal absorption
  • Adverse health effects due to acute exposure include headaches, numbness, sleepiness, nausea, vomiting, and depression of nervous system function
  • Intermediate oral MRL = 0.4 mg/kg/day (liver effects in rats)
  • Oral reference dose = 0.02 mg/kg/day (liver effects in dogs)
  • •Not classifiable as to human carcinogenicity

Chlorodibenzofurans (CDFs) [9-11, 17, 38]

  • Term CDF refers to a group of 135 related chemicals (called congeners) divided into eight subgroups, based upon number of chlorine atoms attached
  • 2,3,7,8-Tetrachlorodibenzofuran (2,3,7,8-TCDF) is most well known, most toxic form of CDFs
  • Formed as a by-product of several industrial processes, also formed during combustion
  • Often found in environment with CDDs, which are structurally related chemicals
  • Forms with fewer chlorine atoms can vaporize and become airborne
  • Forms with more chlorine atoms settle more quickly or adhere to surfaces of particulate matter for eventual deposition on land or in water
  • Does not easily dissolve in water but tends to adhere to soil particles
  • Does not break down easily in air, water, or soil
  • Bioaccumulates in the food
  • Most exposure occurs through ingestion of food with very small amounts of contamination
  • Can also enter body through inhalation or dermal contact
  • Exposure to CDFs can accumulate in fatty tissue over time
  • Wide distribution in the eco-system means that most people have very low background levels of CDFs in their fatty tissue
  • Acute oral MRL = 0.001 µg/kg/day (1 x 10-6 mg/kg/day 2,3,4,7,8-pentaCDF, effects on the thymus in guinea pigs)
  • Intermediate oral MRL = 3 x 10-5 µg/kg/day (3 x 10-8 mg/kg/day 3,4,7,8-pentaCDF, hepatic effects in rats)
  • Inhalation unit risk = 3.8 (µg/m3)-1

Chloroform [9-11, 18, 38]

  • Synthetic chemical
  • Most commonly used in production of other chemicals
  • Liquid at normal temperatures
  • Evaporates easily, dissolves in water easily
  • Does not adhere to soil particles
  • Mostly found in air or in groundwater
  • Can enter body through inhalation, ingestion, dermal absorption
  • Chronic inhalation MRL = 0.02 ppm (97.7 µg/m3) (liver effects in humans)
  • Chronic oral MRL = 0.01 mg/kg/day (liver effects in dogs)
  • Reference dose = 0.01 mg/kg/day (liver effects in dogs)
  • Probable human carcinogen
  • Oral slope factor = 6.1 x 10-3 (mg/kg/day)-1
  • Inhalation unit risk = 2.3 x 10-5 (µg/m3)-1

1,2-Dibromo-3-chloropropane [9-11, 20, 38]

  • Synthetic pesticide
  • Probable human carcinogen
  • Enters body through inhalation, ingestion, and dermal absorption
  • Intermediate oral MRL = 0.002 mg/kg/day (reproductive effects in rabbits)
  • Intermediate inhalation MRL = 0.0002 ppm (1.9 µg/m3) (reproductive effects in rabbits)
  • Inhalation reference concentration = 2 x 10-4 mg/m3 (reproductive effects in rabbits)
  • Inhalation unit risk = 0.002 (µg/m3)-1

1,1-Dichloroethane [9-11, 21, 38]

  • Synthetic chemical
  • Used as a solvent, a degreaser, and to produce other chemicals
  • Evaporates easily from soil and water
  • Breaks down slowly in air, relatively quickly in water
  • Can enter body through inhalation, ingestion, and dermal absorption
  • Adverse health effects in animals due to long-term inhalation exposure at high concentrations include kidney damage and delayed growth in offspring; liver damage; eye and skin irritation; central nervous system depression; drowsiness; unconsciousness
  • Possible human carcinogen
  • Inhalation unit risk = 1.6 x 10-6 (µg/m3)-1

1,1-Dichloroethylene [9-11, 22, 38]

  • Synthetic chemical, most commonly used to make other products
  • Evaporates very quickly from soil and water
  • Breaks down quickly in the air but slowly in water
  • Can enter body through inhalation, ingestion, or possibly dermal contact, most commonly from products containing this chemical
  • Adverse health effects due to chronic inhalation include neurological effects and possible kidney and liver damage
  • Intermediate inhalation MRL = 5 ppm (19,800 µg/m3) (liver effects in guinea pigs)
  • Chronic oral MRL = 0.009 mg/kg/day (liver effects in rats)
  • Oral reference dose = 0.009 mg/kg/day (liver effects in rats)
  • Possible human carcinogen
  • Oral slope factor = 0.6 (mg/kg/day)-1
  • Inhalation unit risk = 5 x 10-5 (µg/m3)-1

1,2-Dichloroethene [9-11, 22]

  • Synthetic chemical used for flame retardants and plastics such as food-packaging films
  • Degrades quickly in air but slowly in water
  • Easily absorbed through lungs, gastrointestinal tract, and possibly skin
  • Adverse health effects include neurological, liver, and kidney effects
  • Intermediate inhalation MRL = 0.02 ppm (79.3 µg/m3) (liver effects in mice)
  • Chronic oral MRL = 0.009 mg/kg/day (liver effects in rats)
  • Chronic oral reference dose = 0.009 mg/kg/day-1 (liver effects in rats)
  • Possible human carcinogen
  • Oral slope factor = 0.6 (mg/kg/day)-1

Dichloromethane (Methylene Chloride) [9-11, 23, 38]

  • Synthetic chemical, widely used in solvents, paint strippers, and other products
  • Evaporates easily but does not easily dissolve in water
  • Enters the body most commonly through inhalation, but also through ingestion and dermal absorption
  • Breaks down slowly in air
  • Chronic oral MRL = 0.06 mg/kg/day (liver effects in rats)
  • Oral reference dose = 0.06 mg/kg/day (liver effects in rats)
  • Inhalation reference concentration = 3,000 µg/m3 (adverse health effects in rats)
  • Probable human carcinogen
  • Oral slope factor = 0.0075 (mg/kg/day)-1
  • Inhalation unit risk = 1 x 10-6 (µg/m3)-1

Ethylbenzene [9-11, 24]

  • Naturally occurring chemical, used in many products
  • Evaporates easily, does not dissolve readily in water
  • Breaks down in air after a few days, especially in the presence of smog and sunlight
  • Can brake down in soil and migrate down to groundwater
  • Can enter body through inhalation, ingestion, and dermal absorption
  • Adverse health effects in animals due to chronic exposure include the possibility of cancer
  • Intermediate inhalation MRL = 0.2 ppm (869 µg/m3) (developmental effects in rats)
  • Chronic oral reference dose = 0.1 mg/kg/day (liver and kidney effects in rats
  • Reference concentration = 1 mg/m3 (developmental effects in rats and rabbits)
  • Not classifiable as to human carcinogenicity

Ethylene Dibromide (1,2-Dibromoethane) [9-11, 25]

  • Small amounts occur naturally, but most is man-made
  • Used as a pesticide and as an additive in leaded gasoline
  • Liquid at normal temperatures
  • Evaporates easily, dissolves in water
  • Breaks down quickly in air, but slowly in soil and water
  • Can enter body through inhalation, ingestion, and dermal absorption
  • Longer term adverse health effects in animals include damage to the lining of the nose
  • Adverse health effects in humans due to inhalation include bronchitis, headaches, and reproductive effects in males
  • Intermediate inhalation MRL = 0.005 ppm (38.4 µg/m3) (respiratory effects)
  • Probable human carcinogen
  • Oral slope factor = 85 (mg/kg/day)-1
  • Inhalation unit risk = 2.2 x 10-4 (µg/m3)-1

Hydrochloric Acid [9-11, 27]

  • Synthetically produced chemical
  • Produced as gas (hydrogen chloride) or as solution in water (hydrochloric acid)
  • Dissolves easily in water
  • Used in metal processing and in manufacture of other products
  • Adverse health effects due to inhalation exposure include eye, nose, and throat irritation, and pulmonary edema
  • Adverse health effects due to contact include severe skin burns and blindness (if contact is in the eyes)
  • Chronic reference concentration = 20 µg/m3

Naphthalene [9-11, 29]

  • Naturally occurring chemical
  • Solid at normal temperatures
  • Has a very strong smell, evaporates easily, breaks down quickly
  • Can dissolve in water and can pass through soil to groundwater
  • Enters body most commonly by inhalation, possibly by ingestion or dermal absorption
  • Intermediate oral MRL = 0.02 mg/kg/day (hepatic effects in mice)
  • Chronic inhalation MRL = 0.002 ppm (10.5 µg/m3) (respiratory effects in mice)
  • Subchronic oral reference dose = 0.04 mg/kg/day (decreased body weight gain in rats)
  • Chronic inhalation reference concentration = 0.003 mg/m3 (respiratory, nose effects in mice)
  • Possible human carcinogen

Styrene [9-11, 30]

  • Synthetic chemical
  • Most commonly used in manufacture of various types of rubbers and plastics
  • Liquid at normal temperatures, evaporates easily
  • Breaks down relatively quickly
  • Can enter body through inhalation, ingestion, and dermal absorption
  • Chronic inhalation MRL = 0.06 ppm (256 µg/m3) (neurological effects)
  • Intermediate oral MRL = 0.2 mg/kg/day (liver effects)
  • Chronic oral reference dose = 0.2 mg/kg/day (hematological, liver effects in dogs)
  • Inhalation reference concentration = 16 mg/m3 (CNS effects in humans)
  • Possible, even probable human carcinogen.
  • Oral slope factor = 0.03 (mg/kg/day)-1

Tetrachloroethylene [9-11, 31, 38]

  • Synthetic chemical used as a dry cleaning fluid, a degreaser, and as a starting material for other products
  • Evaporates quickly, but breaks down very slowly
  • Can travel easily through soils to reach groundwater
  • Inhalation is most common way to enter body, also ingestion if drinking water is contaminated
  • Adverse health effects due to chronic inhalation exposure possibly include reproductive effects in women
  • Higher levels of exposure in animals could cause liver, kidney damage
  • Chronic inhalation MRL = 0.04 ppm (27 µg/m3) (neurological effects in humans)
  • Oral reference dose = 0.01 mg/kg/day (liver effects in mice)
  • Oral slope factor = 0.052 (mg/kg/day)-1
  • Inhalation unit risk = 5.9 x 10-6 (µg/m3)-1

Toluene [9-11, 33]

  • Naturally occurring chemical, also occurs as a result of industrial processes
  • Widely used solvent in many industrial processes and products
  • Enters body through ingestion, inhalation, and dermal absorption
  • Adverse health effects due to intermediate and chronic exposures include fatigue, confusion, weakness, drunken-like actions, memory loss, nausea, and loss of appetite
  • Chronic inhalation MRL = 1 ppm (3,770 µg/m3) (neurological effects in humans)
  • Intermediate oral MRL = 5 mg/kg/day (neurological effects in mice)
  • Oral reference dose = 0.2 mg/kg/day (increased organ weight in rats)
  • Inhalation reference concentration = 0.4 mg/m3 (neurological effects in humans)
  • Not classifiable as to human carcinogenicity

1,1,1-Trichlorethane [9-11, 33]

  • Synthetic chemical
  • Used as a solvent, degreaser, and to make other products
  • Evaporates easily, remains in atmosphere for as long as 6 years
  • Can also migrate to groundwater
  • Can enter body through inhalation, ingestion, and dermal absorption
  • Intermediate inhalation MRL = 0.7 ppm (3,820 µg/m3) (liver effects in gerbils)
  • Not classifiable as to human carcinogenicity

Trichloroethylene [9-11, 34, 38]

  • Synthetic chemical, liquid at room temperature
  • Most commonly used as a degreaser, also in some household products
  • Evaporates readily from surface soil, water
  • Breaks down in air to form phosgene, a lung irritant
  • Breaks down more slowly from deep soils, groundwater
  • Can enter body through inhalation, ingestion, and dermal absorption
  • Adverse health effects due to chronic exposure possibly include childhood leukemia, heart defects, other birth defects
  • Acute inhalation MRL = 2 ppm (10,700 µg/m3) (neurological effects in humans)
  • Intermediate inhalation MRL = 0.1 ppm (537 µg/m3) (neurological effects in rats)
  • Acute oral MRL = 0.2 mg/kg/day (developmental effects in mice)
  • Possible, even probable human carcinogen
  • Oral slope factor = 0.011 (mg/kg/day)-1
  • Inhalation unit risk = 2 x 10-6 (µg/m3)-1

Vinyl Chloride [9-11, 36, 38]

  • Synthetic chemical used in a variety of products, especially PVC (polyvinylchloride) plastic products
  • Gas at ambient conditions
  • Degrades quickly in air to other chemicals that are also toxic
  • Most likely route of exposure is inhalation, though ingestion can also occur
  • Adverse health effects due to chronic inhalation exposures include changes in liver structure, neurological damage, immune reactions, decreased blood flow to extremities, reproductive effects, and cancer
  • Intermediate inhalation MRL = 0.03 ppm (76.7 µg/m3) (liver effects in rats)
  • Chronic oral MRL = 0.00002 mg/kg/day (liver effects in rats)
  • Known human carcinogen
  • Inhalation slope factor = 0.295 (mg/kg/day)-1
  • Oral slope factor = 2.3 (mg/kg/day)-1
  • Inhalation unit risk = 7.8 x 10-5 (µg/m3)-1

Xylenes [9-11, 37]

  • Naturally occurring--and synthetically produced--chemical used in cleaning agents, solvents, paint thinners, and other products
  • Evaporates easily, does not dissolve easily in water
  • Breaks down slowly in soil and groundwater, breaks down relatively quickly in sunlight in air
  • Can enter body most commonly through inhalation, but also through ingestion and dermal absorption
  • Chronic inhalation MRL = 0.1 ppm (434 µg/m3) (neurological effects in humans)
  • Intermediate oral MRL = 0.2 mg/kg/day (blood effects in rats)
  • Oral reference dose = 2 mg/kg/day (hyperactivity, decreased body weight, increased mortality in rats)
  • Not classifiable as to human carcinogenicity

TOXICOLOGICAL EVALUATION OF COMPLETED EXPOSURE PATHWAY

The completed exposure pathways assume that adults and children were exposed to contaminants emitted from the stack of the thermal oxidizer while it was operational. The thermal oxidizer was installed as a part of the USEPA April 1998 emergency response at the Pemaco Site. Its purpose was to destroy volatile organic contaminant vapors in the soil beneath the site.

Thermal oxidizers of the type used at the Pemaco Site pull soil gas vapors from the soil through several vapor extraction wells located around the site. The vapors pass through carbon filters, trapping most of the contamination. The remainder passes into the thermal oxidizer burner, where it burns at a high temperature (>1400 degree Farenheit [°F]). Under optimal operating conditions, virtually all of this contamination is completely consumed, forming only carbon dioxide and water. But small amounts might not be burned, or only partially burned. These unburned or partially burned chemicals can pass through the thermal oxidizer stack and into the atmosphere, or react with other chemicals in the stack or in the atmosphere around the stack to form undesirable byproducts. These unburned or partially burned chemicals and the byproducts they can produce are called Products of Incomplete Combustion (PIC). Two of the more important PICs that can form during combustion are CDDs and CDFs. These are of particular concern because they are very stable in the environment, can accumulate in the tissues of animals and humans, and are probable human carcinogens.

The amount and type of PICs formed in a thermal oxidizer are determined by the operating conditions of the unit and its construction. For example, undesirable byproducts such as CDDs and CDFs are formed within a certain temperature range. To minimize these and other PICs, the thermal oxidizer must be operated outside this temperature range. In addition to operating at the proper temperature, the thermal oxidizer at the Pemaco Site is designed to further minimize the formation of PICs by using a fast flow rate to carry quickly the PICs from the burner to the atmosphere, where their concentration rapidly dilutes. Assuming the thermal oxidizer always operated under optimal conditions, only minute quantities of CDDs and CDFs should have been produced (Personal communication between F.Reber Brown, California Department of Health Services, and Betty Willis, Agency for Toxic Substances and Disease Registry; May 11, 1999). Data on the exact operating conditions are not available, so it is not possible to evaluate accurately the potential for formation of CDDs and CDFs. The Pemaco thermal oxidizer emissions were not tested explicitly for the CDDs or CDFs (Statement by Rose Marie Caraway, Project Manager Pemaco Maywood Site, at Public Meeting at Heliotrope Elementary School; February 20, 1999) [39].

The procedure used to estimate the concentration of pollutants in the emissions from the thermal oxidizer begins with a trial run. During three test runs, concentrations of specific target compounds from the thermal oxidizer stack are measured with four probes at the stack outlet. The results of these three tests for nine target compounds are in Table 7 [2]. The target compounds were total hydrocarbons, benzene, 1,1-dichloroethane, cis-1,2-dichloroethene, ethylbenzene, toluene, vinyl chloride, xylenes, and hydrochloric acid. The emission rate of each target compound was calculated from the concentration of each target compound and the stack flow rate. The computer model uses these emission rates, as well as topographical and meteorological conditions, to predict how emissions from the stack disperse as they are carried by the wind. The concentration of each target compound was calculated at a series of locations along lines radiating from the stack in 10 degree intervals. The points along each line at which the concentration of each target compound was calculated were at 100 meter intervals in the first kilometer, every 500 meters between 1 and 5 kilometers, and every 1,000 meters between 5 and 10 kilometers. In addition to these locations, the concentration of target compounds was explicitly modeled at the Heliotrope Elementary School.

The computer model used to calculate these concentrations was the USEPA ISCT3 model (version 97363) [2]. USEPA Methods 1 and 2 were used to test for stack gas velocity and volumetric flow rate. USEPA Method 3 was used to test for CO2 and O2 gas composition. USEPA Method 26 was used to test for hydrogen chloride plus moisture. USEPA Method 0030 was used to test for VOC concentration. USEPA Method 25A was used to test for total hydrocarbon. USEPA Method 7E was used to test for nitrogen oxides. USEPA Method 10 was used to test for carbon monoxide [2].


 

TOXICOLOGICAL EVALUATION OF INHALATION OF THERMAL OXIDIZER STACK EMISSIONS BY ADULTS AND CHILDREN

The concentrations of target compounds emitted from the thermal oxidizer stack were modeled at a series of locations surrounding the Pemaco Site, including the neighborhood south of the site. The peak annual concentration occurred at a point approximately 100 meters east-northeast of the site. A person at that location is referred to as the Maximum Exposed Individual (MEI). The concentration of emissions from the thermal oxidizer stack was also calculated specifically at the Heliotrope Elementary School. This location was chosen as a place where children--a sensitive receptor population--are located for several hours each day. The concentration of the emitted target compounds at the MEI and the Heliotrope School is shown in Table 8.

We evaluated the cancer and non-cancer effects of the modeled air concentrations. The increased lifetime cancer risk is calculated by multiplying the unit risk by the concentration of that chemical in the air. The unit risk is a measure of a chemical's ability to cause cancer. When more than one cancer-causing chemical is present, the increased lifetime cancer risk for each is added together as the total increased lifetime cancer risk. A total increased lifetime cancer risk that is less than 1 x 10-6 is generally considered not significant.

The total increased lifetime cancer risk at each location is less than 1 x 10-6 (1.2 x 10-7 and 8.7 x 10-9 for the MEI and Heliotrope School, respectively) (Table 8). 1,2-Dibromo-2-chloropropane is the primary contributor to this total increased lifetime cancer risk (1.1 x 10-7 and 8.3 x 10-9 at the MEI and Heliotrope School, respectively). Therefore, based on these data, the lifetime cancer risk does not significantly increase for individuals exposed at either the Heliotrope School or the MEI. Similarly, the lifetime cancer risk does not significantly increase due to exposure to emissions from the thermal oxidizer in the neighborhood south of the site.

Non-cancer health effects are evaluated by comparing the modeled air concentration to the reference concentration (RfC). The RfC is the concentration of that chemical in the air to which a person could be exposed without adverse health effects. The hazard quotient is the ratio of the measured (or calculated) concentration to the reference concentration. A hazard quotient of less than or equal to 1 means that the measured (or calculated) concentration is less than or equal to the reference concentration. Thus, adverse health effects would not be expected, even in an exposed person. The hazard index is the sum of the hazard quotients for the chemicals of interest.

The hazard index for the target compounds at both locations is less than 1 (Table 8). The largest contributor in each location is 1,2-dibromo-3-chloropropane (0.28 and 2.1 x 1-0-4 for the MEI and Heliotrope School, respectively). Therefore, based on these modeled data, non-cancer adverse health effects would not be expected to occur in individuals exposed at either the Heliotrope Elementary School or the MEI. Similarly, one would not expect non-cancer adverse health effects to occur in the residents of the neighborhood south of the site due to exposure to emissions from the thermal oxidizer.

Because they were not among the target compounds tested, no modeling is available for dioxins. Also, this evaluation is contingent upon the operating parameters of the thermal oxidizer, such as temperature and flow rate maintained at optimal settings at all times during operation. If the thermal oxidizer operated outside its optimal conditions, the potential for the formation of PICs increases. Indeed, some community groups have expressed concern that this type of thermal oxidizer is not routinely operated at peak efficiency, and as a result, substantial amounts of PICs are released into ambient air.


ATSDR CHILD'S HEALTH INITIATIVE

In communities faced with contamination in their water, soil, air, or food, ATSDR recognizes that infants and children can be more sensitive to exposures than adults. This sensitivity is a result of a number of factors. Children are more likely to be exposed to soil or surface water because they play outdoors and often carry food into contaminated areas. Children can come into contact with and ingest soil particles at higher rates than adults do. Also, some children with a behavior trait known as "pica" are more likely to ingest soil and other non-food items. Children are shorter than adults, which means they can breathe dust, soil, and any vapors close to the ground. Also, because they are smaller, they have higher doses of chemical per body weight.. The developing body systems of children can sustain permanent damage if toxic exposures occur during critical growth stages. Finally, because most children depend completely on adults for risk identification and management decisions, ATSDR is committed to evaluating their special interest at applicable sites as a part of the ATSDR Child Health Initiative. In this health assessment, children were considered as a separate receptor population from adults. For instance, screening levels for children were used to evaluate the environmental data in this risk assessment.


LIMITATIONS OF TOXICOLOGICAL EVALUATIONS

Incomplete data is a problem often encountered during the evaluation process. Of the many thousands of commonly used chemicals, relatively few have been thoroughly evaluated for toxicity. Some information is missing for most chemicals. Information on the non-carcinogenic adverse health effects of a particular chemical might be available, but not information as to its potential to cause cancer. Information regarding the toxicity of a chemical for short exposures at high concentrations--such as what could occur in the workplace--might be found easily, but information regarding its toxicity at low concentrations for long periods of time might be almost nonexistent. In these situations, researchers cannot evaluate completely the health implications of exposures.

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